Water Quality Compliance Specification

Transcription

1 Water Quality Compliance Specification MRWA Specification No Construction and Connection of New Drinking Water & Non Drinking Water Mains

2 Disclaimer "The Water Agencies exclude all liability to all persons and all conditions and warranties, which are expressed or implied at law (including under statute). Where liability and conditions and warranties cannot be excluded at law, the liability of the Water Agencies is limited at their choice, to resupplying MRWA Specification No or paying the cost of resupplying MRWA Specification No Please note that MRWA Specification No or information contained within the Specification shall only be used in conjunction with the Melbourne Retail Water Agencies Edition of the Water Services Association of Australia (WSAA) Water Supply Code of Australia WSA , 3.1. Document History The following information indicates the changes made to this document. Issue Revision Date Approved Paragraph Change Reason for Change 1.0 A st edition of the water quality compliance specification 2.0 A May 2012 Amended to include water quality compliance for non drinking water 2.0 B July 2012 Amended to include updated water parameter limits Appendix 1-Table 2 Inclusion of non drinking water parameter limits Updates to the drinking water microbiological parameter limits 2.0 C October 2012 Amended to include updated water parameter limits Appendix 1-Table 2 Additional Updates to the drinking water microbiological parameter limits MRWA Specification No Rev C Page 2 of 16 24/10/2012

3 Contents 1 Purpose Drinking Water: Non Drinking Water Scope 4 3 Quality Criteria 5 4 Basic Requirements 5 5 Preventative Measures Keeping Pipe Clean and Dry Storage Temporary Capping Jointing, Packing and Sealing Materials Approved Products Cleaning Methods Disinfection and neutralisation of disinfectant Safety Sampling Sample Set No A Existing Main Sample Set No B New Main Tests 10 9 Test Results All results Sample Set No A (existing) and Set No B (new mains) Non-compliant results for Sample Set No A existing main Non-compliant results for Sample Set No B New main For microbiological quality: For chemical and physical quality: Notification References 11 Appendix 1- Water Quality Parameter Limits 13 Appendix 2- Approved Laboratories and Analysis 15 Appendix 3 - Flowchart Water Quality Compliance for New Mains 16 MRWA Specification No Rev C Page 3 of 16 24/10/2012

4 1 Purpose 1.1 Drinking Water: All new drinking water supply and non drinking water (ie: recycled water) supply mains need to demonstrate compliance with the Water Agency s water quality compliance standards This specification has been established to define the joint Melbourne Retail Water Agency (MRWA representing City West Water, South East Water and Yarra Valley Water) deem-to-comply water quality compliance requirements. Many new water mains are constructed each year to service new development or replacement/renewal of existing assets. The water quality from new mains shall comply with Water Agency Licence requirements before the water is suitable for human consumption, i.e. it shall be safe, clear and free from objectionable taste and odour. The Australian Drinking Water Guidelines, the Victorian Safe Drinking Water Act 2003 and Regulations 2005 all focus on the Water Agency maintaining risk management plans for the water supply system from the catchment to the customer s tap. This specification is part of the Water Agency s risk management plan and follows the Hazard Analysis and Critical Control Point (HACCP) principles by reducing risks to hazards/contamination and verifying that the water quality is compliant with the Water Agency requirements before a new main is accepted into service and the drinking water is made available for consumption. 1.2 Non Drinking Water 2 Scope The Water Agencies all maintain Hazard Analysis and Critical Control Point (HACCP) for non drinking water schemes and this specification forms part of the risk management plan reducing risks to hazards/contamination and verifying that the non drinking water quality is compliant with the Water Agency requirements before a new main is accepted into service and the non drinking water main is made available for use. New water mains (including drinking water and/or non drinking water shall be constructed to minimize the risk of contamination of the water. The water from new mains shall be tested for compliance with water quality parameters for drinking water and/or non drinking water, as defined within Appendix 1, before the main can be accepted for service. The provisions of this specification shall apply to both drinking water and non drinking water mains.water mains greater than or equal to (>=) 225mm diameter shall be disinfected prior to sampling and testing. MRWA Specification No Rev C Page 4 of 16 24/10/2012

5 3 Quality Criteria The water from all disinfected mains shall be neutralised before discharge to the environment. Preventing contamination from entering a main is a most important step when constructing a new water main. The requirements for prevention of contamination and for mains cleaning are provided in Clause 5. The physical, chemical and microbiological test results on the samples collected verify that the quality of the water to be supplied from the new water main is suitable for its intended use. The Water Agency requirements for water quality test results are provided in Appendix 1. The collection and testing of water samples shall be completed by an independent NATA accredited laboratory employing a drinking water analyst approved by the Victorian Department of Health for analysing E. coli and turbidity, refer to Appendix 2. All sample results shall be issued in accordance with NATA s accreditation requirements. The locations for the sampling of water shall be identified on the design plans submitted to the Water Agency for approval. The Water Agency or an independent approved water mains disinfection contractor shall be used to disinfect >= 225 mm diameter mains to achieve a minimum chlorine contact time (CT) value (refer to details in Clause 6). 4 Basic Requirements Prevent contaminating materials from entering the water main during storage, construction and connection. This has the added benefit of reducing the amount of water required for swabbing/flushing and the amount of disinfectant required. Remove any contaminating materials by swabbing and flushing the water mains. Disinfect water mains > = 225 mm diameter, using an independent approved contractor, to achieve a minimum CT value (refer to Clause 6 below). Neutralise the disinfectant before it is discharged to the environment. Determine the physical, chemical and microbiological quality by having an independent approved laboratory sample and test the water from identified locations on the existing and new water main/s. Provide water quality test results as evidence that the water quality complies with the requirements. MRWA Specification No Rev C Page 5 of 16 24/10/2012

6 Carry out further mains cleaning works on the main/s to rectify non-complaint test results and re-sample and test if required, until all test results comply. 5 Preventative Measures Preventing contamination of the drinking water in all parts of the water supply system from catchment to customers tap is the focus of the risk management plans/haccp plans maintained by the Water Agency. It is essential that the requirements of this Clause be followed to reduce the risks of contamination. Preventing contamination at this early stage of an asset s life is relatively easy and low cost because it is the last time the asset is readily accessible. 5.1 Keeping Pipe Clean and Dry Storage Pipe delivered for construction shall be stored and handled so as to minimise entrance of foreign materials. Delay in placement of delivered pipes invites contamination. The more closely the rate of delivery is related to the rate of pipelaying, the less likelihood of contamination. Fittings stored either on site or in storage shall be boxed, capped or sealed with plastic wrapping Temporary Capping During and after pipelaying operations, the contractor shall supply and use exclusion caps, plugs or blank flanges of approved design to seal all open ends of pipes and fittings at all times Jointing, Packing and Sealing Materials No contaminated material or any material capable of supporting growth of microorganisms shall be used within the pipe. Materials or gaskets shall be handled in a manner, which avoids contamination. The jointing lubricant used shall be approved for use in potable water and delivered to the site in closed containers which are to be kept in a clean condition at all times Approved Products Only products that comply with AS/NZS 4020 for use in contact with potable water and approved by the Water Agencies shall be used in the construction of the water mains. 5.2 Cleaning Methods All new mains > = 100 mm diameter, shall be swabbed to remove any deleterious material. Swabbing shall be carried out in accordance with Clause 18 of the MRWA Edition WSA All mains, including those that are swabbed and mains that are less than 100mm diameter (i.e. typically 40 mm, 50 mm, or 63 mm) shall be flushed at high flow for 5 minutes minimum for every 100 metres of main or part thereof (note that a MRWA Specification No Rev C Page 6 of 16 24/10/2012

7 fully open hydrant with average system hydraulic pressure will flow at minimum 10 litres per second). A high flow is required to generate a water velocity that will re-suspend, carry and discharge small particulate material. Mains greater or equal to 225 mm diameter shall be disinfected after swabbing. Refer to Clause 6 for details. Large mains above 750 mm diameter can be manually cleaned in stages by sweeping and hosing and sealing after completion of all internal works and prior to disinfection. 6 Disinfection and neutralisation of disinfectant Disinfection of water mains is to be carried out by an approved contractor. Water mains > = 225 mm diameter shall be disinfected using chlorine as the disinfectant in the form of sodium hypochlorite solution. The disinfectant is to be added to the new water main via a suitable injection point just downstream (within 3 metres) of the connection of the new main to the existing main a hydrant is a suitable injection point. The discharge point for disinfection will be at the end of the new main(s) and will be from a hydrant or other suitable control valve fitted with a portable flow meter to measure discharge flow. The disinfectant is injected into the main when there is a known water flow via a discharge flow meter. This flow should be adjusted to match the disinfectant dose. The flow of disinfectant into the new main will be calculated to achieve a minimum continuous dose of > = 5 milligrams per litre (mg/l) of chlorine. The injection of the disinfectant should stop when the free chlorine residual (FCR) in the discharge water is > = 5 mg/l. The disinfected new main shall be isolated from the existing supply for backflow prevention during the contact period by closing the control valve as appropriate. The disinfectant shall stay in the new main for a minimum contact time of at least 1 hour to achieve a minimum CT value of 5 milligram hours per litre (i.e. 5 mg/l of chlorine for a 1 hour period, or 2.5 mg/l of chlorine for 2 hours). The FCR shall then be measured at half hour intervals. Note that the measured FCR in the discharge water will decrease with time. The contact time should therefore continue until the minimum CT value is achieved refer to table 1 below. At the end of the contact time, the chlorine in the water in the new main shall be neutralised before the water is discharged to the environment. MRWA Specification No Rev C Page 7 of 16 24/10/2012

8 One method of neutralising the chlorine is to add Sodium Thiosulphate to the water as it is being discharged from the main. If this method is used, FCR measurements shall be taken of the discharge water to confirm zero or at least < 0.1 mg/l chlorine levels to verify neutralisation. An alternative neutralising method is to capture the disinfected water and contain it on site to allow the chlorine to dissipate. A minimum of 2 days containment period is suggested before the water should be allowed into the environment but again only when the FCR is zero or at least < 0.1 mg/l. Records should be kept of: a) the volume of water in the main to be disinfected, b) the volume of disinfectant, c) the FCR at end of dosing, d) the FCR at half hour intervals until end of contact time, e) the contact time, f) the neutralisation method used, g) three FCR measures during the sodium thiosulphate method, h) the containment period and, i) one FCR measure at the end of the on site containment method. 6.1 Safety Chlorine disinfectants and chlorine neutralising agents are harmful substances manufacturer s specification and Material Safety Data Sheets shall be followed when using, storing, handling, etc. MRWA Specification No Rev C Page 8 of 16 24/10/2012

9 Table 1 Minimum contact time for the disinfectant based on the lowest measured free chlorine residual (FCR). The contact time is proportionally based on a minimum CT value of 5 mg hours/l. Chlorine Residual (C) mg/l at time T Minimum Contact Time (T) hours 5.0 or greater 1 hour hours hours hours hours hours hours 7 Sampling Water samples shall be collected from the identified locations by an independent approved laboratory (refer to Appendix 2) after final swabbing / flushing / hydrostatic pressure testing and disinfection and neutralisation and temporary connection to the existing main. The consultant shall record the exact location of each sample site for appropriate referencing by the laboratory and for the Water Agency. At least one sample for each Sample Set shall be collected. Refer to the flowchart of the sampling/testing process shown in Appendix Sample Set No A Existing Main One sample shall be taken from a front garden tap at a property already supplied from the existing main, provided: (a) the sample location is located within 500 metres of the connection point and; (b) permission from the property owner has been obtained. If it is not possible to take a sample from a front garden tap at a property on the existing main, a fire hydrant on the existing main can be used after it has been flushed at a minimum flow of 0.5 litres per second for a minimum of 5 minutes. The sample collected from the existing main is to be taken from the main that was used to charge the new main i.e. if the new non drinking water main was filled/charged from the drinking water main, then the drinking water main is to be sampled to represent the existing main. MRWA Specification No Rev C Page 9 of 16 24/10/2012

10 7.2 Sample Set No B New Main 8 Tests 9 Test Results A minimum of one sample shall be taken at the mid point of the feeder main, located centrally within project. If a project has more than five (5) sub mains and/or dead end mains an extra sample will be taken for every 5 th sub main/dead end. The total number of samples will be spread out along the feeder main. If one or more of the samples fails to meet the specified water quality parameter limits, each selected sub main/dead end shall be retested to the required parameters set out in section 9.5. If any services are available, this is the first preference for sampling from. If it is not possible to take a sample from a service or tapping point on the new main, a fire hydrant on the new main can be used after it has been flushed at a minimum flow of 0.5 litres per second for a minimum of 5 minutes. The consultant will identify on the design plans the location for the samples to be taken and provide appropriate sample location reference for the laboratory and the Water Agency. The Water Agency can direct more and/or alternative sample locations. The water samples shall be tested by an independent approved laboratory (refer to Appendix 2) for the physical, chemical and microbiological parameters specified in Appendix 1 using NATA accredited methodology. Refer to the flowchart of the sampling/testing process shown in Appendix 3. The MRWA water quality testing parameters for Drinking Water (Table 2) and Non-drinking Water mains (Table 3) are defined within Appendix All results Sample Set No A (existing) and Set No B (new mains) The water quality results will be satisfactory if they are within the limits for all parameters specified in Appendix 1. The Water Agency shall be notified if any sample contains E. coli immediately after the result is available. The consultant shall notify the Water Agency of all results as detailed in Clause Non-compliant results for Sample Set No A existing main For test results outside the limits specified in Appendix 1, the Water Agency will carry out rectification works on the existing main to ensure that the water quality complies with the limits before the new main is accepted into service.

11 9.3 Non-compliant results for Sample Set No B New main For test results outside the limits specified in Appendix 1, the consultant will carry out rectification works on the new main to ensure that the water quality complies with the limits before the new main is accepted into service. These works will depend on the results as follows: 9.4 For microbiological quality: The main/s shall be flushed or swabbed and flushed (as per Clause 5 above), and if required, disinfected, until the follow up samples for both the new and existing main comply with all parameters. 9.5 For chemical and physical quality: 10 Notification 11 References Arrange for follow up samples for both the new and existing main/s and test for the parameter/s that failed. If the follow up sample/s comply with the limits then no further works are required. If the follow up sample/s fail again then the new main/s shall be flushed, swabbed and flushed (as per Clause 5 above) until further follow up sample/s for both the new and existing main comply with all parameters. The Water Agency shall be notified by the consultant if any sample contains E. coli immediately after the result is available. The laboratory will also directly notify the Water Agency immediately. Any non-compliant results for the other parameters shall be reported to the Water Agency within 24 hours of being available. A copy of the test results with sample site references shall be provided by the consultant to the Water Agency with the construction verification form and ideally within 48 hours of results becoming available. A copy of any non-compliant results will also be automatically sent to the Water Agency directly by the laboratory. A copy of the records for disinfection and neutralisation (refer to Clause 6) shall be provided by the consultant to the Water Agency with the construction verification form. Water Industry Act 1994 Water Agency Licence for Provision of Water and Sewerage Services Safe Drinking Water Act 2003 Safe Drinking Water Regulations 2005 MRWA Specification No Rev C Page 11 of 16 24/10/2012

12 Australian Drinking Water Guidelines 2004 (NHMRC) Hazard Analysis and Critical Control Point (HACCP) guidelines AS/NZS 4020 Testing of products for use on contact with drinking water MRWA Specification No Rev C Page 12 of 16 24/10/2012

13 Appendix 1 Drinking Water Quality Parameter Limits Table 2 This table refers to either the drinking water or non drinking water new mains where the new main has been charged by the existing drinking water main. Parameter Units Sample Set A Existing Main Water Agency Limits PHYSICAL PARAMETERS Sample Set B New Main Water Agency Limits ADWG Recommended Limits ph Units > 6.5 and < 9.2 A ± 0.5 < 6.5 and > 9.2 Apparent Colour HU <= 20 < ( A + 5) ~25 Turbidity NTU <= 3 < ( A + 0.5) 5 EC us/cm < 200 < ( A + 50) ~1250 CHEMICAL PARAMETERS Free chlorine residual mg/l < 1.0 A ± Total chlorine residual mg/l < 1.0 e.g. 0.4 A ± 0.2 e.g MICROBIOLOGICAL PARAMETERS E. coli orgs/100 ml < 1 < 1 < 1 Total coliforms orgs/100 ml 200 orgs/100ml < 2 x A if the result is greater than 20 orgs/100ml < 200 # Heterotrophic Plate count orgs/ml 1000 orgs/100ml < (5 x A ) if the result is greater than 100 orgs/100ml < 1000 # # = these limits are advisory as there is no specific recommended limits in ADWG

14 Non Drinking Water Quality Parameter Limits Table 3 This table refers to Non drinking water mains where the new non drinking water main has been charged by an existing non drinking water main. Parameter Units Sample Set A Existing Main Water Agency Limits PHYSICAL PARAMETERS Sample Set B New Main Water Agency Limits ph Units > 6.5 and < 9.2 A ± 0.5 Apparent Colour HU <= 70 < ( A + 5) Turbidity NTU <= 3 < ( A + 0.5) EC us/cm < 1200 < ( A + 50) CHEMICAL PARAMETERS Free chlorine residual Total chlorine residual mg/l < 1.5 A ± 0.2 mg/l < 1.5 e.g. 0.4 MICROBIOLOGICAL PARAMETERS E. coli orgs/100 ml < 1 < 1 Notes: A ± 0.2 e.g. 0.6 ADWG = Australian Drinking Water Guidelines (NHMRC) A = the actual test result for the relevant parameter for Sample Set No A (existing main) HU = Hazen Units NTU = Nephelometric Turbidity Units µs/cm = (microsiemens per centimetre) mg/l = milligrams per litre orgs/100 ml = organisms per 100 millilitres orgs/ml = organisms per millilitre

15 Appendix 2 Approved Laboratories and Analysis An independent approved laboratory is one that has NATA accreditation for all parameters listed in Appendix 1 and employs drinking water analysts approved by the Victorian Department of Health for analysing E. coli and turbidity parameters pursuant to the Safe Drinking Water Regulations (SDWR) For a list of approved Drinking Water Analysts and Laboratories refer to the Department of Health Victoria website (Refer to guidance note 5) MRWA Specification No Rev C Page 15 of 16 24/10/2012

16 Appendix 3 Flowchart Water Quality Compliance for New Mains Start Construct the water main, then swab, flush and pressure test as required Disinfect main if >= 225 mm and neutralise disinfectant Consultant arranges sample collection at identified locations or as requested by Water Agency Approved laboratory takes samples and carries out testing Re-flush, swab, disinfect as required (or other appropriate remedial action) Is E coli present in any sample? Yes Water Agency to rectify Consultant to rectify No No Yes Is the sample from the existing system? Are other physical, chemical and microbiological results OK? No Notify Water Agency immediately for E.coli or within 24 hours for other parameters Yes Forward all test results to water agency within 48 hours Finalise connection, then commission new main when Water Agency has approved Water Agency inputs results to Water Quality database, and investigates any anomalies, as required End MRWA Specification No Rev C Page 16 of 16 24/10/2012